Mourners at the funeral of Shane Clancy, in South Dublin, were told the young man had been "overtaken by darkness" last Sunday and had brought "great tragedy to two other lovely families as well as his own".
This morning's funeral, at the Church of the Assumption, Dalkey, followed a fatal stabbing attack carried out by Mr Clancy in Bray, Co Wicklow when he killed 22-year-old design student Sebastian Creane and seriously injured his brother Dylan Creane and Jennifer Hannigan.
Parish priest Fr John McDonagh said only a few professionals would ever understand the "destructive frenzy" that had occurred last weekend.
Chief mourners at the funeral were Mr Clancy's parents Patrick and Leonie, stepfather Tony, his four brothers, two sisters, grandmother and extended family and friends. Also among the packed congregation, were many of his classmates and colleagues from Trinity College Dublin, where he was studying Irish and Biblical and Theological studies.
Fr Paddy Gleeson, chaplain of the college, was also present.
Prayers were said for the Clancy family as well as the families of Mr Creane and Ms Hennigan. The congregation was also asked to pray for all those suffering from depression.
Mr Clancy stabbed to death Sebastian Creane at the Creane family home in Cuala Grove, Bray, Co Wicklow, in the early hours of last Sunday morning after a night out. Mr Creane’s girlfriend Jennifer Hannigan, and his brother Dylan, were also stabbed by Mr Clancy, but survived.
After carrying out the stabbings just after 4.30am, Mr Clancy went to the back garden of the Creane house, where his remains were later found. He had been stabbed in the chest and a knife was found with the body. Gardaí are not seeking anybody else in relation to Mr Clancy’s death.
Gardaí believe Mr Clancy murdered Mr Creane because Mr Creane had begun seeing Mr Clancy’s former girlfriend, Jennifer Hannigan, from Killiney, south Dublin.
The Irish Timeshas established from Garda sources and local sources in south Dublin that Mr Clancy had in recent weeks become increasingly preoccupied with the ending of his relationship with Ms Hannigan. They had dated each other for about three years and broke up earlier this year.
Mr Clancy had recently tried repeatedly to contact a large number of people on social networking sites that he did not know personally, but who he knew were friends of Ms Hannigan. A number of people had informed Ms Hannigan of this and it is believed she had asked her friends to do nothing that would encourage any further contact with Mr Clancy.
Sources said that in recent weeks Mr Clancy had repeatedly made contact with Ms Hannigan via mobile calls and text.
He had also begun approaching friends of Ms Hannigan inquiring about her, despite the fact he did not personally know the people he was approaching.
Mr Clancy had been suffering from depression and was being treated for this, according to some sources. He had recently withdrawn from a planned trip to do charity work abroad.
Despite being in the same group socialising on Saturday night, Sebastian Creane and Mr Clancy were not friends. Mr Creane (22) had gone out with two friends, all former students at St Gerard’s in Bray, to the Eagle House pub in Sandycove.
Dylan Creane and Jennifer Hannigan are recovering in hospital.